At present, rotation mechanisms used to enable the rotation of a motor vehicle seat around a perpendicular axis can be split into two types according to rotation medium, namely rolling rotation mechanisms and sliding rotation mechanisms. In a rolling rotation mechanism, multiple hard balls which have been set in a retaining frame in advance are used as the rotation medium, enabling a moving plate to rotate in an annular track formed by an upper row of balls and a lower row of balls. In order to increase separation strength, an upper anti-detachment hook is mounted on the moving plate, and a lower anti-detachment hook is mounted on a fixed plate; when subjected to a force, the upper and lower anti-detachment hooks hook into each other, and are used to enhance the anti-separation function of the rotation mechanism.
The technical solution described above is known art in this field; reference may be made to Chinese invention patents CN 106427682 A and CN 97114364.1.
Referring to FIG. 1, a ball and ball track force-bearing structure in CN 106427682 A is worthy of discussion. Upper steel balls 1 are radially offset from lower steel balls 2 by an amount AA; under a pressing action, a ball track surface 4 of a moving plate 3 has the tendency to deform downwards, with the lower steel balls 2 beneath as a pivot point and AA as an arm of force, i.e. the relationship between the upper steel balls 1 and the lower steel balls 2 is unable to achieve a cancellation effect whereby two forces are equal in magnitude and opposite in direction. Furthermore, under a pressing action, a locking claw 5 has the tendency to come out of a locking hole 6 in the moving plate 3 and a locking hole 9 in a press plate 7 (the press plate 7 being connected in a fixed manner to a fixed plate 8), and under a pulling action, the lower steel balls 2 have the tendency to leave a ball track. The former will give rise to a safety problem; the latter is a functional problem, and is worthy of improvement here.
Referring to FIG. 2, upper steel balls 10 and lower steel balls 11 in CN 97114364.1 are also affected by the problem which affects patent CN 106427682 A.
In the case of a luxury MPV, referring to FIGS. 3 and 4, there is an ever-increasing number of fittings on an independent middle-row seat 12 (with increased weight); at the same time, in order to meet comfort needs, two fixing points which were previously mounted on the vehicle body are fitted to the seat—this is a so-called ABTS seat. Such a structure, in which all three fixing points are on the seat, places higher demands on the rotation mechanism in terms of anti-separation strength, which is generally 2000 Nm or more. In the known art, the separation strength is increased through the engagement of upper anti-detachment hooks 13 with lower anti-detachment hooks 14; however, since the lower anti-detachment hooks 14 are four independent lower anti-detachment hooks 14, and since the four independent lower anti-detachment hooks 14 are disconnected from one another, it is very difficult for the four lower anti-detachment hooks 14 to act in synergy. If the upper anti-detachment hook 13 detaches from one of the lower anti-detachment hooks 14, the entire structure will rapidly collapse; unless the hook contact area is increased, it will be very difficult to break through the 2000 Nm bottleneck. A squeezing effect on a moving plate ball track is formed between two steel balls, i.e. a lower steel ball serves as a pivot point for a moving plate rolling surface.
Furthermore, referring to FIG. 1, a height H of a conventional rolling rotation mechanism in a perpendicular direction is high, because in general, an anti-detachment hook 5 between the moving plate 3 and the press plate 7 must be riveted or connected by bolts, and tool space for riveting and torque guns places requirements on the height H. At the same time, space must also be left for movement of a pawl, and the moving plate and press plate must both have high folded edges. Generally, the height H is 45 mm or more.
In the prior art described above, a conflict exists between increasing the separation strength and reducing the height H of the rolling rotation mechanism in the perpendicular direction, because in order to increase the separation strength, it is necessary for an action surface of the anti-detachment hook to be designed to be higher, and the corresponding rotation mechanism height will also become higher.
After adjustment of a seat rotation mechanism, a fixed plate and a moving plate are fixed by means of a locking device. Referring to FIG. 1, in the case of a locking device in CN 106427682 A, the locking claw 5 is flipped down and inserted into the locking hole 5 in the moving plate 3 and the locking hole 9 in the press plate 7 (the press plate 7 being connected in a fixed manner to the fixed plate 8). Since the locking claw 5 is mounted on the moving plate 3, and in order to arrange the locking hole 6 and the locking hole 9, edges of the moving plate 3 and the press plate 7 must extend upward, forming high folded edges 15 and 16, and resulting in a thick overall profile.
Referring to FIGS. 5 and 6, in the case of another locking device disclosed in CN 103863151 in the prior art, the locking device 17 is positioned between a fixed plate 18 and a moving plate 19, and a tooth-shaped element 20 is translationally inserted into and withdrawn from slots 21, 22 between the moving plate 189 and the fixed plate 18 to achieve locking. Such a design reduces the design height of the rotation mechanism.
Referring to FIG. 7, CN 1189343 C in the prior art discloses a similar locking device; the locking device 23 is also mounted between a fixed plate 24 and a moving plate 25. Specifically, a tooth-shaped element 26 is pulled manually, and the tooth-shaped element 26 is rotationally inserted into and withdrawn from locking holes 27, 28 between the moving plate 25 and the fixed plate 24 to achieve locking.
All of the locking devices in the known art described above employ one-piece claw-shaped or tooth-shaped members, i.e. are realized by jamming several successive protrusions into corresponding successive slots.
As is well-known, due to the effects of manufacturing precision, in the case of a profile formed by multiple polygonal line segments at different angles, profiles in actual and theoretical states cannot be completely coincident; the greater the number of protrusions, the greater the degree of non-coincidence. Two protruding/recessed components are matched to each other, and this non-coincidence is a superposition relationship, hence zero-gap fitting is always impossible; this is the problem of so-called free play, and is an intrinsic characteristic of the structure.
In the known art, unlocking operations have poor ergonomics; passengers must turn a handle from one side to achieve unlocking, but lifting the hand to achieve unlocking would have a more natural feeling and require less effort. Although a rotary handle can be changed to a pull-up handle through the use of a harness for unlocking, this has the disadvantages of low transfer efficiency, and structural redundancy.